JP2006266153A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable injection hole injection valve in which deposits are prevented from adhering to a sac chamber at a bottom end of a valve body, an inner surface of an injection hole, and the vicinity of an outlet of the injection hole.
SOLUTION: A valve body, a sac chamber disposed at a bottom end of the valve body, a first nozzle hole group and a second nozzle hole group disposed in the valve body for injecting fuel, And a first injection mode for injecting only from the first nozzle hole group according to an operating condition of the internal combustion engine, comprising: one or more on-off valves that open and close the first nozzle hole group and the second nozzle hole group; A fuel injection valve that switches between a second injection mode injecting from both the first nozzle hole group and the second nozzle hole group, wherein the sac chamber and the combustion chamber are provided at the bottom of the tip of the valve body. And a valve member that is disposed so as to close the communication hole from the inside of the valve body and opens the communication hole by an in-cylinder pressure of the combustion chamber. Variable injection hole injection valve.
[Selection] Figure 1

Description

  The present invention relates to a common rail fuel injection valve for an internal combustion engine. More specifically, the present invention relates to a fuel injection valve (hereinafter referred to as “variable injection hole injection valve”) in which the injection hole area (number of injection holes) increases in accordance with the lift amount of the needle valve.

In the direct injection type diesel engine, the shape and the injection amount of the fuel spray injected from the fuel injection valve have an optimum state in each of the engine operating state and the early and late stages of the injection. As a method for realizing this, there are conventional techniques disclosed in Patent Document 1 and Patent Document 2, for example. This is because the tip of the valve body is provided with one or more needle valves that selectively open and close the upper and lower two-stage nozzle holes. A more appropriate injection rate can be realized by injecting fuel from the hole.
Hereinafter, in a fuel injection valve, opening a nozzle hole at any stage by a needle valve is referred to as "valve opening", and closing a nozzle hole at any stage by a needle valve is referred to as "valve closing". That's it.

  On the other hand, in a normal fuel injection valve (not a variable injection hole area) of such a direct injection type engine, since the fuel injection valve faces the combustion chamber, the fuel injection valve heated by combustion or the flame during combustion As a result, the fuel is carbonized on the inner surface of the nozzle hole or in the vicinity of the nozzle hole outlet to generate a so-called deposit. The main components of this deposit are carbon (C), oxygen (O), sulfur (S), calcium (Ca), etc., and the deposit accumulates on the surface of the injection hole with time, and the fuel metering performance and There is a problem of impairing the spray performance.

  To solve this problem, for example, Patent Document 3 discloses a technique of applying an oil-repellent coating around the nozzle hole to prevent fuel adhesion around the nozzle hole.

JP 2004-11526 A JP 2004-241370 A JP 2002-364498 A

  FIG. 5 shows a cross-sectional view of the above-described normal fuel injection valve (hereinafter referred to as “normal injection valve”) in a non-injection state. In the normal injection valve 400, in the injection state, when the needle valve 20 is raised, high-pressure fuel flows from the fuel reservoir 13 into the injection hole 11 and the sac chamber 12, and further through the injection hole 11 to the engine. It ejects to the combustion chamber 31. That is, every time an injection is performed, new fuel flows from the fuel reservoir 13 into the sac chamber 12 and is ejected to the engine combustion chamber 31 through the nozzle hole 11. Therefore, even if deposits are attached to the inner surface 11a of the nozzle hole 11 and the surface 12a of the sac chamber 12, the deposits are washed each time with new fuel, and the deposit accumulation can be suppressed to a certain extent.

  On the other hand, an example of the aforementioned variable injection hole injection valve is shown in FIG. FIG. 4 shows a cross-sectional view in the first injection mode in which the integral needle valve 20 performs an intermediate lift and the injection is performed only from the first injection hole group 15. Normally, the first injection mode is used for initial injection, after injection, and partial load injection.

  A sliding inner peripheral portion 10b is disposed at the bottom end of the valve body 10, and a sliding outer peripheral portion 20d is disposed at the distal end portion 20a of the integrated needle valve 20, and the sliding inner peripheral portion is provided. The diameter gap between 10b and the sliding outer peripheral portion 20d is, for example, a minute gap of 0.5 to 2 μm and plays a role of a sealing function.

  When the integral needle valve 20 is further lifted from the intermediate lift position and is fully lifted, the second nozzle hole group 16 is opened and is in communication with the sac chamber 12. Then, the high-pressure fuel in the fuel reservoir 13 flows into the sac chamber 12 via the communication hole 20c provided in the needle valve tip 20a, and a part of the fuel accumulated in the sac chamber 12 is injected into the second jet. It flows into the hole group 16 and further jets into the engine combustion chamber 31. At this time, since the injection from the first injection hole group 15 is continuously performed, the injection is made from both the first injection hole group 15 and the second injection hole group 16. This is the second injection mode. Usually, the second injection mode is used for main injection at high load.

However, in a vehicle engine, partial load operation often continues for a long time, and in the case of an engine equipped with a variable injection hole injection valve, the first injection mode continues for a long time. At this time, since the second injection hole group 16 is closed by the sealing function of the sliding portions 10b and 20d, the fuel accumulated in the sac chamber 12 continues to stay for a long time. As a result, the staying fuel receives the residual heat from the combustion chamber 31 for a long time and is converted into a resin (pitched) or oxidized to form a deposit, which adheres to and accumulates on the sac chamber surface 12a. As this adhesion and deposition progresses, the deposit wraps around the gap between the sliding portions 10b and 20d, and eventually closes the inlet of the second nozzle hole group 16. If so, injection from the second injection hole group 16 in the second injection mode is inhibited, or the sliding outer peripheral portion 20d of the tip end portion of the needle valve is baked to destroy the sealing function of the sliding portion.
That is, the variable injection hole injection valve has a structure in which the surface of the sac chamber is not washed with new fuel each time unlike the normal injection valve, and deposits are very easily generated.

  An object of the present invention is to provide a variable injection hole injection valve that suppresses deposit adhesion to the sac chamber at the bottom end of the valve body, the inner surface of the injection hole and the vicinity of the outlet of the injection hole.

According to invention of Claim 1,
The high-pressure fuel supplied from the fuel supply pump is accumulated in the common rail, and the high-pressure fuel accumulated in the common rail is injected into the combustion chamber of the internal combustion engine,
A valve body, a sac chamber disposed at the bottom of the tip of the valve body, a first nozzle hole group and a second nozzle hole group disposed in the valve body for injecting fuel, and the first nozzle hole A group and one or more on-off valves for opening and closing the second nozzle hole group,
Switching between a first injection mode injecting only from the first nozzle hole group and a second injection mode injecting from both the first nozzle hole group and the second nozzle hole group in accordance with the operating conditions of the internal combustion engine. A fuel injection valve,
The sac chamber has a structure in which fuel is retained during the first injection mode, and a part of the fuel in the sac chamber is injected from the second injection hole group during the second injection mode,
A communication hole that communicates the sac chamber and the combustion chamber with the bottom of the tip of the valve body, and the communication hole that is disposed so as to close the communication hole from the inside of the valve body. A fuel injection valve is provided.

  The prior art has only a coating of an oil-repellent film as described in Patent Document 3 and is used for depositing fuel that stays in the sac chamber of the variable injection hole injection valve for a long time by continuing partial load operation. Was almost powerless. On the other hand, the fuel injection valve according to claim 1 allows the sac chamber fuel at the bottom end of the valve body to pass through the communication hole that connects the sac chamber and the combustion chamber for the following reason during the next engine compression stroke. It is discharged into the engine combustion chamber. For this reason, the sac chamber is emptied, and the fuel does not stay in the variable injection hole injection valve sac chamber for a long time and is not deposited.

That is, during the first injection hole closing, a small amount of sac chamber fuel leaks from the first injection hole through the needle valve tip communication hole and the fuel reservoir under the seat. As a result, the valve member receives the same sac chamber fuel pressure as the combustion chamber pressure. Due to the increase in the in-cylinder pressure due to the next compression stroke, the pressure in the valve body communication hole also increases. For this reason, the valve member that has closed the valve body communication hole moves to the needle valve tip side and opens. As a result, the sac chamber fuel flows into the combustion chamber at once through the valve body tip portion communication hole, and the sac chamber is emptied.
The sac chamber fuel that has flowed into the combustion chamber immediately before the explosion combustion by the regular fuel spray is vaporized in the combustion chamber and burned together with the regular fuel spray.

According to invention of Claim 2,
An oil repellent film is formed on at least a part of the surface of the sac chamber, the surface of the valve member, the inner surface of the injection hole, the inner surface of the communication hole, and the outer surface of the distal end portion of the valve body, A fuel injection valve characterized in that the fuel injection valve according to claim 1 is provided.

  In addition to the effect of the invention according to claim 1, the fuel injection valve according to claim 2 further forms an oil repellent film that repels fuel deposits at a place where deposits are likely to occur, and the occurrence of deposits at the places. It can be set as the structure which suppresses.

  According to the present invention, it is possible to obtain a variable injection hole injection valve that suppresses deposit adhesion to the sac chamber at the bottom of the valve body tip, and further to the inner surface of the injection hole and the vicinity of the outlet of the injection hole.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a fuel injection valve according to Embodiment 1 of the present invention, FIG. 2 shows a fuel injection valve according to Embodiment 2 of the present invention, and FIG. 3 shows an operation explanatory view of a valve member of the embodiment of the present invention. For reference, FIG. 4 shows a conventional variable injection hole injection valve, and FIG. 5 shows a normal injection valve. In all the following drawings, the same function is denoted by the same number.

FIG. 1 shows a cross-sectional view of a fuel injection valve 100 according to Embodiment 1 of the present invention in a first injection mode.
10 is a valve body, 10a is a valve body seat portion, 10b is a sliding inner peripheral portion of the valve body, 12 is a sac chamber, 13 is a fuel reservoir, 14 is a fuel reservoir under the seat portion, 15 is a first nozzle hole group, 16 is The second nozzle hole group, 17 is a valve body tip portion communication hole, 20 is an integral needle valve, 20a is a needle valve tip portion, 20b is a needle valve seat portion, 20c is a needle valve tip portion communication hole, and 20d is a needle valve tip. A sliding outer peripheral portion, 31 is an engine combustion chamber, and 41 is a valve member.

  In the first injection mode, the needle valve 20 performs an intermediate lift and injects only from the first injection hole group 15. The second nozzle hole group 16 is closed by a needle valve tip sliding outer peripheral portion 20d. Further, since the sac chamber 12 communicates with the fuel reservoir 13 through the under-seat fuel reservoir 14 and the needle valve tip communication hole 20c, it receives a common rail fuel pressure. For this reason, the valve member 41 is pressed against the valve member seat portion 17 a to close the valve body tip portion communication hole 17. The valve member 41 is a ball valve, and the valve member seat portion 17a is a conical surface.

  At the time of partial load, the engine is operated only in the first injection mode. When the first injection mode ends, the needle valve seat portion 20b is seated on the valve body seat portion 10a. Thereafter, a small amount of fuel in the sac chamber 12 having the common rail fuel pressure leaks to the engine combustion chamber 31 through the communication hole 20 c and the first injection hole group 15. The fuel pressure in the sac chamber 12 is the same as the engine combustion chamber pressure.

FIG. 3 is an operation explanatory view of the valve member according to the fuel injection valve of the present invention. In FIG. 3, the vertical axis represents the in-cylinder pressure, which is the engine combustion chamber pressure, and the horizontal axis represents the crank angle. The fuel staying in the sac chamber 12 in the injection 1 receives the in-cylinder pressure that rises in the vicinity of the crank angle θ ₁ before the injection 2 through the communication hole 17, and the valve member 41 moves from the seat portion 17 a to the needle valve tip 20 a It leaves in the direction and rises to the maximum lift position 41a indicated by the broken line. As a result, the communication hole 17 is opened, and the fuel in the sac chamber 12 flows out to the engine combustion chamber 31. Thereby, deposit generation is suppressed. Even in this lifted state, the ball valve 41 has a shape and dimension that cannot be completely detached from the conical surface of the valve member seat portion. Therefore, when the sack chamber 12 is filled with fuel in the next injection stroke, the ball valve 41 Returns to the position where the communication hole 17 is closed again and stops.

  When the valve member 41 is lifted to the maximum, the sac chamber 12 communicates with the engine combustion chamber 31 through both the communication hole 17 and the first injection hole group 15. Leaks.

  Further, at least one of the sac chamber surface 12a, the surface of the valve member 41, the inner surfaces of the first injection hole 15 and the second injection hole 16, the inner surface of the communication hole 17, and the distal end portion outer surface 10c of the valve body 10 An oil repellent film is partially formed. The oil repellent film is, for example, a fluorine material coated at 10 μm to 50 μm, and fuel adhesion can be prevented by the oil repellent property of the fluorine material, and thus the formation of deposits can be suppressed.

  FIG. 2 shows a cross-sectional view in the first injection mode of the fuel injection valve according to Embodiment 2 of the present invention. 10 is a valve body, 10a is a valve body seat part, 12 is a sac chamber, 13 is a fuel reservoir, 14 is a fuel reservoir under the seat part, 15 is a first nozzle hole group, 16 is a second nozzle hole group, and 17 is a valve body tip. A part communication hole, 21 is a first needle valve for opening and closing the first injection hole 15, 22 is a second needle valve disposed inside the first needle valve 21 for opening and closing the second injection hole 16, and 22a Is a second needle valve tip portion, 22c is a second needle valve tip portion communication hole, 31 is an engine combustion chamber, 41 is a needle roller type valve member, and 42 is a valve member spring.

  As shown in FIG. 2, the first needle valve 21 and the second needle valve 22 as the injection hole opening / closing valve are slidably combined with each other, and the first needle valve 21 is in the full lift position. The lift amount of the second needle valve 22 is zero. The needle roller type valve member 41 is slidably disposed in the T-shaped communication hole 22c at the tip portion of the second needle valve, and is urged by the valve member spring 42 so as to be pressed against the valve member seat portion 17a. ing. Without this valve member spring 42, when the second needle valve 22 is opened, the fuel that has flowed into the sac chamber 12 raises the valve member 41, causing a problem that the fuel flows out from the communication hole 17.

  The sac chamber 12 is filled with fuel that has entered from the gap between the T-shaped communication hole 22 c and the needle roller type valve member 41.

  At the time of partial load, the engine is operated only in the first injection mode. When the first injection mode ends, the first needle valve seat portion 21b is seated on the valve body seat portion 10a. Thereafter, a small amount of fuel in the sac chamber 12 having the common rail fuel pressure leaks into the engine combustion chamber 31 through the communication hole 22 c and the first injection hole group 15. The fuel pressure in the sac chamber 12 is the same as the engine combustion chamber pressure.

  The reason why the hole 22c is a T-shaped communication hole and not an I-shaped non-communication hole is that when the valve member 41 is pushed toward the second needle valve tip 22a by the in-cylinder pressure, the fuel behind the hole is formed. This is because the valve member 41 is less likely to move due to the dashpot effect in which is compressed.

As shown in FIG. 3, the fuel accumulated in the sack chamber 12 in the injection 1 receives the increased in-cylinder pressure through the communication hole 17 in the vicinity of the crank angle θ ₁ before the injection 2, and the seat It separates from the portion 17a toward the second needle valve tip 22a and floats up. As a result, the communication hole 17 is opened, and the fuel in the sac chamber 12 flows out to the engine combustion chamber 31. Thereby, deposit generation is suppressed. Due to the fuel flowing in from the T-shaped communication hole in the next injection stroke, the valve member 41 returns to the position where the communication hole 17 is closed again and stops.

It is sectional drawing in the 1st injection mode of the fuel injection valve by Embodiment 1 which concerns on this invention. It is sectional drawing in the 1st injection mode of the fuel injection valve by Embodiment 2 which concerns on this invention. It is a figure explaining the action | operation of the valve member which concerns on the fuel injection valve of FIG.1 and FIG.2. It is sectional drawing in the 1st injection mode of the conventional variable injection hole injection valve. It is sectional drawing of the conventional fuel injection valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Valve body 10a Valve body sheet | seat part 10b Valve body front-end | tip sliding inner periphery 10c Valve body front-end | tip outer surface 11 Injection hole 11a Injection hole inner surface 12 Suck chamber 12a Sack chamber surface 13 Fuel reservoir 14 Under-seat fuel reservoir 15 1st injection Hole group 16 Second nozzle hole group 17 Valve body tip portion communication hole 17a Valve member seat portion 20 Integrated needle valve 20a Needle valve tip portion 20b Needle valve seat portion 20c Needle valve tip portion communication hole 20d Needle valve tip sliding outer peripheral portion 21 First Needle Valve 22 Second Needle Valve 31 Engine Combustion Chamber 41 Valve Member 42 Valve Member Spring 100 Variable Injection Hole Injection Valve 200 of Embodiment 1 Variable Injection Hole Injection Valve of Embodiment 2 300 Conventional Variable Injection Hole Injection Valve 400 Normal injection valve

Claims (2)

The high-pressure fuel supplied from the fuel supply pump is accumulated in the common rail, and the high-pressure fuel accumulated in the common rail is injected into the combustion chamber of the internal combustion engine,
A valve body, a sac chamber disposed at the bottom of the tip of the valve body, a first nozzle hole group and a second nozzle hole group disposed in the valve body for injecting fuel, and the first nozzle hole A group and one or more on-off valves for opening and closing the second nozzle hole group,
Switching between a first injection mode injecting only from the first nozzle hole group and a second injection mode injecting from both the first nozzle hole group and the second nozzle hole group in accordance with the operating conditions of the internal combustion engine. A fuel injection valve,
The sac chamber has a structure in which fuel is retained during the first injection mode, and a part of the fuel in the sac chamber is injected from the second injection hole group during the second injection mode,
A communication hole that communicates the sac chamber and the combustion chamber with the bottom of the tip of the valve body, and the communication hole that is disposed so as to close the communication hole from the inside of the valve body. A fuel injection valve comprising: a valve member that opens the valve.   An oil repellent film is formed on at least a part of the surface of the sac chamber, the surface of the valve member, the inner surface of the injection hole, the inner surface of the communication hole, and the outer surface of the distal end portion of the valve body, The fuel injection valve according to claim 1.

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